Retailers generally avoid publicizing their Black Friday specials far in advance because of the potential of hurting sales before the big day arrives. Who, for instance, would buy a 42-inch plasma screen RCA TV for $450 today when they know it’ll be on sale for $199 in a couple of weeks?

Yet shoppers are already facing such scenarios, thanks to the widespread proliferation of leaked Black Friday ads. (The TV deal mentioned above is, in fact, featured in a leaked Black Friday brochure for Kmart.) For weeks, sites such as bfads.net, FatWallet, BradsDeals, gottadeal.com, and dealnews have been posting scanned copies of dozens of Black Friday brochures for retailers like Staples, Sears, Best Buy, Macy’s, Walgreens, Cabela’s, Bed Bath & Beyond, Sam’s Club, and more.

Over 30 leaked Black Friday ads for major retailers have already surfaced online, and we still have two-plus weeks to go before Black Friday is actually here. Do these ads represent the real deal on Black Friday deals? They probably do, though in the past, leaked brochures have turned out to be fakes or early versions that wound up being tweaked before officially being released to the public. So no one should bank on a leaked ad showing exactly the same items at the same prices found in stores on Thanksgiving or Black Friday.

Are retailers upset by the early, supposedly unauthorized leakage? In many cases, yes. At least they say they are. As USA Today reported, some retailers send out “cease and desist” letters to websites posting leaked ads, or just ask sites to take them down. The websites, which get the ads in a variety of ways—cellphone photos of print shop workers, e-mails from anonymous sources many suspect to be marketers for the retailer—tend to simply post the ads and wait for something to happen:

“If the ad stays up for more than a few hours, it’s most likely implicit that the retailer is fine with it being public,” says Brent Shelton, spokesman for FatWallet.com. “Of course, they may have just missed the ad leaking right away or their process for a C&D may take longer than others.”

Because leaked ads amount to free publicity for stores, there’s good reason for retailers to allow the brochures to stay up. It appears as if some stores are responsible for unofficial leaks, and it’s certain that some stores are responsible for official leaks—or “previews,” as they’re called. Lowes, for instance, has already released a preview of items that’ll be on sale throughout Black Friday weekend. Last year, Walmart went ahead and posted its Black Friday specials on its Facebook page two weeks in advance. For the 2012 holiday season, Walmart has posted its Black Friday sales online two weeks ahead for all to see as well.

A dealnews post about Black Friday ad leaks explained that while retailers don’t want information to leak too early—that’ll give the competition more than enough time to react—they also are known to use leaks to build excitement and attract shoppers:

Some retailers will offer sneak peaks or perks (such as early ad releases) for shoppers who sign up for email alerts, “Like” a Facebook page, or follow the store on Twitter; this is precisely what Walmart did last year. This tactic allows retailers to gather information about shoppers, build email or distribution lists, and secure Black Friday shoppers. All combined, this dangling of information is a retailer’s second most compelling sales trick, after the deals themselves. It’s all part of the plan to drive sales and loyalty — and get attention.

What about the deals themselves? Judging by what’s been leaked (released?), it appears they’ll be the usual mix of eye-popping bargains, decent values, and so-so prices. Often in these ads, the amount one saves is way overstated.

While it’s impossible to verify where the leaked ads come from or which of them are legitimate, there’s one thing we can all bank on—and it’s that Black Friday, and the entire holiday shopping season, will be full of pricing shenanigans like this.